An IGBT (Insulated gate bipolar transistor), a MOSGTO (Metal oxide gate turn-off thyristor) or the like is a so-called voltage drive type semiconductor device which can control current by voltage applied on an insulated gate, and is widely used in a power source or an inverter with a bipolar transistor of current drive type.
In recent, that is used largely in an inverter for a hybrid electric vehicle (HEV). Following the diversification of hybrid electric vehicles, various inverters having different output current values are provided.
Generally, the capacity of transistor driving an inverter with small capacity is small, and the capacity of transistor driving an inverter with large capacity is large.
As a driving device constituting an inverter of an IGBT, a direct drive type driving device (see the Japanese Patent Laid Open Gazette 2001-223571) or an indirect drive type driving device which is current amplification type is used.
For the inverter of the IGBT with small capacity, either of the direct drive type driving device and the indirect drive type driving device is used. However, for the IGBT with large capacity, the indirect drive type driving device is often used and the direct drive type driving device is rarely used.
That is because the size of the driving device constructed to be an IC chip becomes large by building the transistor with large capacity in the chip, thereby increasing the cost. That is also because the exothermicity of the transistor for large current is large so that the radiation of heat is difficult.
As the direct drive type driving device, generally, the driving device having a MOS transistor as the switch device such as a driving device of direct drive 1 shown in FIG. 6 or the driving device having a bipolar transistor as the switch device such as a driving device of direct drive 2 shown in FIG. 7 is used.
As the indirect drive type driving device, generally, the driving device having a MOS transistor as the switch device and a bipolar transistor as the switch device for current amplification which is an external member such as a driving device of indirect drive 1 shown in FIG. 8, the driving device having a bipolar transistor as the switch device and a bipolar transistor as the switch device for current amplification which is an external member such as a driving device of indirect drive 2 shown in FIG. 9, the driving device having two external inverters connected in series each of which is constructed by a MOS transistor so as to amplify current such as a driving device of indirect drive 3 shown in FIG. 10, or the driving device having one external inverter which is constructed by a MOS transistor so as to amplify current such as a driving device of indirect drive 4 shown in FIG. 11 is used.